The present invention relates to a process for the selective removal of acetylenic and carbonyl impurities, especially acetylenic impurities, from gaseous streams without significantly affecting the recovery of the desired hydrocarbons. The process of this invention is particularly useful for the removal of acetylenic impurities from gaseous streams of organic compounds.
The terms “acetylenes” or “acetylenic impurities” are used interchangeably herein to denote acetylene, vinyl acetylene, methyl acetylene, ethyl acetylene and the like. Such compounds are often found as impurities in various organic product streams. For example, the oxidative or non-oxidative dehydrogenation of C4-C8 hydrocarbons having at least one
grouping to produce the corresponding ethylenically unsaturated hydrocarbons produces small amounts of acetylenes. Similarly, in the production of olefinic hydrocarbons by the cracking of hydrocarbon feed streams, certain quantities of acetylenes are produced. Some ethylene recovery processes, for example, the cuprous salt method, necessitate that the acetylenes be first removed, since acetylene reacts with the cuprous ions to form an explosive compound. Furthermore, ethylene utilized for the purpose of polymerization requires an almost total removal of acetylenes.
Thus, a great effort has been expended to develop methods for removing acetylenes from organic streams, particularly C2-C8 paraffinic and olefinic hydrocarbons. Two approaches have been employed (1) physical, involving distillations, extractions, extractive distillation and various combinations of physical processes and (2) catalytic. In the former process, if the concentration of acetylenic impurities is high, it may reach dangerous levels where detonation can occur. Thus, catalytic approaches have generally been preferred.
Some catalytic approaches in the art are described U.S. Pat. Nos. 3,476,824; 3,728,412; 4,009,126; 4,075,256; 4,083,887; 4,513,159; 4,658,080; and United States Patent Application Publication No. US 2004/0122275 which disclosures are incorporated herein in their entirety. Some of the catalytic processes involve hydrogenating the acetylenic impurities back to alkenes and alkanes. However, this approach could result in some loss of the desired alkenes and alkadienes.
Thus, it would be preferable to find a process for selectively removing most of the acetylenic impurities (e.g., at least 80%, preferably at least 95%) from a gaseous stream without significantly affecting the recovery of the monoolefins and diolefins, particularly the desired diolefins. It would be preferable to recover at least 95% of the desired diolefins in the process.